Ganong's Review of Medical Physiology, 23rd Edition

CHAPTER 2Overview of Cellular Physiology in Medical Physiology 41

FIGURE 2–10 Rough endoplasmic reticulum and protein translation. Messenger RNA and ribosomes meet up in the cytosol for transla-
tion. Proteins that have appropriate signal peptides begin translation, then associate with the endoplasmic reticulum (ER) to complete translation.
The association of ribosomes is what gives the ER its “rough” appearance. (Reproduced with permission from Widmaier EP, Raff H, Strang KT: Vander’s Human
Physiology: The Mechanisms of Body Function, 11th ed. McGraw-Hill, 2008.)

Cytoplasm

Extracellular fluid

mRNA from Gene A mRNA from Gene B

Free ribosome

Signal sequence

Rough

endoplasmic

reticulum

Growing

polypeptide

chain

Carbohydrate

group

Cleaved signal

sequences

Vesicle

Golgi apparatus

Secretory vesicle

Plasma membrane

Exocytosis

Digestive

protein

from

Gene B

Lysosome

Secreted protein

from Gene A